Question

I’m trying to add two extra config options to my application.rb so I can read them out in controllers.

# Extra
config.twitter.key = 'foo'
config.twitter.secret = 'bar'

I am trying to access them using three suggested methods:

self.config.twitter.key # Should be extended through ApplicationController Base
config.twitter.key # Inherited but with different syntax
CONFIG['twitter']['key'] #some massive magical array that apparently exists somewhere

They all give me different kinds of error when I pass them through the “debug” method, E.g:

debug self.config.twitter.key # undefined method `key' for nil:NilClass

So, whats going on?

Answer 1

I believe you’ve got a slightly incorrect idea behind what your expectations for the config/application.rb is providing you. The ActiveRecord::Base and ActiveController::Base eigenclasses use the Rails::Application::Configuration class that is configured in config/application.rb. The attributes aren’t available in classes that descend from either of the Base classes, nor their eigenclasses. This is why you are running into errors in ApplicationController.

There are generally two ways to make configuration initializations in a Rails app. The first way is to create a configuration module and then load values into it via initializer:

First, create a Twiter Config module:

#lib/twitter_config.rb
module TwitterConfig
  def self.config
    @@config ||= {}
  end

  def self.config=(hash)
    @@config = hash
  end
end

Create a YAML config file:

# config/twitter.yaml
development: &base
  key: "foo"
  secret: "bar"

test:
 <<: *base
 key: "foo2"

production:
  <<: *base
  secret: "barbar"

Alternatively, if you don’t intend to add config/twitter.yaml to your SCM, you can just skip this and set the key and secret via environment variables. This would be the suggested solution for an application with a public SCM repository deploying on Heroku.

Then load and set the value via an initializer:

#config/initializers/01_twitter.rb
require 'twitter_config'

TwitterConfig.config = YAML.load_file("config/config.yml")[Rails.env].symbolize_keys

It’s generally a best practice to number your initializer files as Rails will load them in order according to their filename. If you are initializing a datastore and that is critical for other steps, then it needs the lowest number. Alternatively, if you are using environment variables, this would be the init file:

#config/initializers/01_twitter.rb
require 'twitter_config'

TwitterConfig.config[:key] = ENV['twitter_config_key']
TwitterConfig.config[:secret] = ENV['twitter_config_secret']

Throughout the Rails application, you now have access to the config values with TwitterConfig.config[:key] & TwitterConfig.config[:secret]. You can include the module as well, just watch out for conflicts.

You can also just load the values as a global constant. It feels a bit ugly to me though:

#config/application.rb
TWITTER_CONFIG = YAML.load_file("config/twitter.yaml")[Rails.env]